He studied from 1537 to 1542 at the University of Wittenberg, where the humanistic theology of Philipp Melanchthon made a strong impression on him.

In 1574 he published Syntagma institutionum christianarum, but was obliged to retract it in 1576 following pressure from Augustus, Elector of Saxony to suppress Crypto-Calvinism.

[4] He wrote that most of the Devil's power came through illusions and that witches only did physically impossible things in dreams, like flying on brooms.

In 1579 Frederick II suspended Hemmingsen from his teaching role at the University of Copenhagen after representations from his brother-in-law, Augustus, Elector of Saxony, husband of Anne of Denmark.

[5] Hemmingsen met James VI of Scotland at Roskilde on 11 March 1590 and they had a long discussion or debate in Latin on theological issues and predestination.